Lithography is used in the manufacture of integrated circuits. It is used to transfer circuit patterns from a mask to silicon (or other equivalent and alternative) surfaces. In recent times, for optical lithography at least, the characteristic wavelength has decreased from 365 nm (nanometers) to 248 nm to 193 nm and is currently migrating to 157 nm. At a 157 nm wavelength, for example, features could be printed at a resolution of 100 nm and maybe even at a 70 nm level using phase-shift masks and optical proximity correction.
EUV light can further extend optical lithography by using wavelengths in the range of 11 to 14 nm, allowing for shrinkage of feature size. For example, a 13.5 nm EUV system could theoretically print features much less than 30 nm. Operation at such extremely short wavelengths, presents a number of problems. Some of these problems have to do with optical absorption, requiring the use of reflective materials instead of refractive ones; others have to do with optical contamination, requiring a vacuum environment. Still other problems arise in power production, where an EUV source cannot produce but a fraction of the suggested manufacturing power output, which may be on the order of at least 100 watts of power at the entrance of the optics system or intermediate focus. To solve at least the last of these problems, it would be advantageous to provide various plasma-based EUV light source mechanisms, where, for example, the desired EUV wavelength could be used at a desired power output level in, for example, lithography.